Motor and sensor magnets
Custom ring and tube magnets
EMTXI supplies custom neodymium (NdFeB) ring and tube magnets for motors, pumps, micro-turbines, magnetic couplings and sensors, from prototype quantities to recurring series. Based in Belgium, we compare suitable production routes for your drawing and return feasibility, price, lead time and the documentation that goes with it. We do not manufacture; we manage the route from drawing to delivery.
Start with the dimensions that matter
Give the outer diameter, inner diameter and height, and mark which of them are functional. The wall thickness — half the difference between outer and inner diameter — decides more about feasibility and price than any other number. Add the sample quantity and the expected annual volume. An existing part number, or a sketch with dimensions, is enough to start.
Magnetisation decides the route
| Magnetisation | Poles | Usual route |
|---|---|---|
| Axial | On the two flat faces | Sintered NdFeB; the most common and simplest ring |
| Diametral | On opposite sides of the outer surface | Sintered NdFeB oriented across the diameter |
| Radial | On the inner and outer surfaces | Radially oriented sintered rings in limited sizes; larger diameters are usually built from arc segments |
| Multipole | Several north and south poles around the ring or on one face | Usually bonded NdFeB or ferrite; sintered rings case by case, depending on orientation and magnetising fixture |
Mark the direction, the number of poles, and whether the rings should be delivered magnetised. Our magnetisation guide explains the terms.
Thin walls
There is no universal minimum wall: it depends on diameter, height and tolerances. As a rule of thumb, sintered NdFeB walls below about 1.5 mm need a case-by-case feasibility check. They are fragile, need extra grinding and careful handling, and increase scrap and price. If the wall can grow, say so. If it cannot, a bonded ring is often the more robust choice.
Sintered or bonded
| Sintered NdFeB | Bonded NdFeB | |
|---|---|---|
| Magnetic strength (Br) | About 1.1–1.45 T, depending on grade | About 0.45–0.75 T, depending on process |
| Thin walls and complex shapes | Possible; fragile below about 1.5 mm | Well suited (pressed or injection-moulded) |
| Multipole magnetisation | Case by case | Straightforward |
| Tooling | Usually none for machined rings | Press or mould tool for series |
| Temperature | 80–200 °C, depending on grade | Limited by the binder |
Rings in water and humid environments
NdFeB corrodes without protection. Nickel-copper-nickel (NiCuNi) suits dry and humid indoor use. Epoxy or parylene coatings, or encapsulation in plastic, protect better against permanent contact with water. For drinking-water applications, the materials in contact with water must be suitable for that use; the approval route belongs to the manufacturer of the end product. We quote coating and encapsulation options and supply the producer's material declarations. See coatings.
Tolerances
Ground dimensions are typically held to ±0.05 mm; tighter tolerances are possible at extra cost. State whether dimensions apply before or after coating, and specify concentricity or perpendicularity where they matter. See tolerances.
What we need to quote
Outer diameter, inner diameter, height and the functional dimensions (a drawing if available)
Magnetisation: axial, diametral, radial or multipole (number of poles); delivered magnetised or not
Grade, or the required Br and HcJ and the maximum operating temperature
Environment: dry, humid, water, drinking water, chemicals
Coating or encapsulation, if specified
Sample quantity and expected annual volume
Delivery country and target date
Buyer questions
Do you have standard ring sizes in stock?
We do not hold stock. Custom sizes are made to order. Where your design allows, we can propose a nearby size that a producer already makes, which usually shortens lead time and lowers cost.
What lead time should I expect?
Grades without dysprosium or terbium — most N grades — typically take a few weeks from approved drawing to delivery. Heat-resistant grades (H, SH, UH) usually contain Dy or Tb; from China they need an export licence, which can add two to four months. We quote the route and lead time per order. See export licences.
Can you supply rings for drinking-water applications?
We can quote coatings and encapsulation suited to permanent water contact, and provide the producer's material declarations. Approval of the finished product for drinking water remains with its manufacturer.
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